Ventilated ceiling construction



Mb: 1%? A. NESHER ETAL VENTILATED CEILING CONSTRUCTION 4 Sheets-Sheet 1Filed Feb. 11, 1965 Feb. M, 1%? A. NESHER ETAL.

VENTILATED CEILING CONSTRUCTION V 4 Sheets-Sheet 2 Filed Feb. 11, I965 1I n" Fw M1, W? men-am izA'AL VENTILATED CEILING CONSTRUCTIONSheets-Sheet 5 Filed Feb. ll, 1965 wll I United States Patent 3,303,771VENTILATED CEILING CONSTRUCTION Alexander Nesher, Rosemont, John K.Henderson, Villauova, and Robert J. Sigel, Narberth, Pa., assignors toRobert J. Sigel, Inc., Nat-berth, Pa., a corporation of PennsylvaniaFiled Feb. 11, 1965, Ser. No. 431,831 Claims. (Cl. 9840) This inventionrelates .generally to ceiling constructions and particularly to animproved false sealing construction for a room.

Manufacturing facilities providing the environmental control necessaryfor the manufacture of todays sophisticated components and systems areknown as clean rooms. A clean room is a space in which airbornecontamination, and if needed, temperature and humidity are controlled toa far higher degree than conventional air conditioned areas. Oneapproach to the design and operation of a clean room utilizes highlyfiltered and conditioned air brought into the room through a filter bankcovering an entire wall or ceiling of the room, and exhausted through asimilar entire surface. The air is moved through the room in a laminarflow fashion, thus making only a single pass through any given area ofthe room. This laminar flow air movement quickly carries any releasedcontamination brought into the room on personnel and equipment, andairborne contamination generated by operations in the room, out of theroom. Contamination generated in localized areas of the room is isolatedfrom other areas by the striations of the luminar air flow. Emphasis isplaced on performing critical work in the undisturbed flow of clean airfrom the incoming air surface. Personnel restrictions, equipment, andoperational limitations are minimized.

When a room is provided with a false ceiling, it is quite common toutilize the plenum chamber formed between the false ceiling and the trueceiling as a supply duct for ventilating air, which flows from theplenum chamber downwardly to the room through perforations provided inthe false ceiling. But the flow of ventilating air through a ceilingthat is merely perforated is non-uniform and turbulent. A laminar airflow room requires a uniform flow of filtered air uniformly distributedthroughout the room so that turbulence is reduced to a minimum. Therequirements for a laminar air flow room are set forth in FederalStandard No. 29, Clean Room and Work Station Requirements, ControlledEnvironment. Until the appearance of Federal Standard No. 29, ventilatedceilings were designed only for ordinary air conditioning or ventilatinginstallations, and therefore ventilating rates only ranged up to 5c.f.m. of air per square foot of ceiling area. A laminar air flow roomrequires a much higher rate. Accordingly, an important object of thepresent invention is to provide a false ceiling construction having amaze of nozzles distributed over the entire ceiling area for shower-likedelivery of ventilating air at an increased rate from a plenum chamberto the room below in a uniform non-turbulent distribution pattern.

Another object of the invention is to provide such a ceilingconstruction which directs the air flow in a downward vertical patternonly at a ventilating rate in the order of 150 c.f.m. of air per squarefoot of ceiling area.

Another object of the invention is to provide such a ceilingconstruction which gives almost prefect uniformity of air distributionwhen air is introduced at only one end of comparatively large rooms.

Another object is to provide such a ceiling construc tion comprising anopen framework and a system of air diffuser panels carried thereby.

Another object is to provide such a ceiling construc- "ice tion whereineach panel is a one-piece sheet-like member of thermoplastic materialformed integrally with panel stiffening corrugations.

Another object is to provide such a ceiling construction wherein for agiven pressure in the plenum chamber and a given flow of ventilatingair, the size and number of nozzles per unit of ceiling area arepredetermined.

Other objects of the invention will become apparent when the followingdescription is read with reference to the accompanying drawings, inwhich:

FIGURE 1 is a diagrammatic perspective view of a clean room, part of thetrue ceiling being broken away to show a false ceiling construction inaccordance with the invention;

FIGURE 2 is an enlarged vertical section on line IIII in FIGURE 1;

FIGURE 3 is a section on line IIIIII in FIGURE 2;

FIGURE 4 is a section on line IVIV in FIGURE 3;

FIGURE 5 is a perspective view looking at the top of an air diffuserpanel;

FIGURE 6 is a perspective View looking at the bottom of a diffuserpanel;

FIGURE 7 is an enlarged perspective view of one corner of a dilfuserpanel, as viewed from the top;

FIGURE 8 is an enlarged perspective view of one corner of a diffuserpanel, as viewed from the bottom; and

FIGURE 9 is a diagram showing a family of performance curves.

The following description is directed to the specific form of theinvention illustrated in the drawings and is not intended to beaddressed to the scope of the invention itself, which may be practicedin a variety of forms.

Referring particularly to FIGURE 1, four upright walls, designated 10,rest upon a true floor 12 and support a true ceiling 14 from which issuspended a false ceiling 16 disposed over a room 18. Between the falseceiling 16 and the true ceiling I4 is a plenum chamber 20 into which airmay be conducted through a duct 22. Air entering the plenum chamber 20through the duct 22 passes through the false ceiling 16 into the room 1%below and out of the room through an open grille type floor 24, raisedabove the true floor 12 to form a plenum 25. The air flows out of theplenum 25 through the duct 27. The direction of air flow is shown byarrows.

The false ceiling 16 comprises an open framework, generally designated26, which framework includes a pair of rolled angle members 28 and apair of rolled angle members 36 secured to the walls 1%, as by nails 32.Bridging the members 28 are a set of laterally spaced T-bar members 34,and bridging the members 30 and the T-bars 34 are short T-bar members36. The members 28, 30, 34 and 36 are secured together to afford a rigidopen framework which is suspended from the true ceiling 14 by means ofsuitable hangers 38. The openings in the framework are designated 40 inFIGURES 2, 3 and 4.

Referring particularly to FIGURES 2 to 8, a diffuser panel 42constructed in accordance with the invention is a thin, sheet-likerectangular member made of thermoplastic material, which may be opaque,translucent or transparent. Preferably, the panel is made of apolyvinyl. The panel is provided with a peripherally extending flange,generally designated 44, having a planar outer rim area 46 and an innerarea 48 inclined relative to the plane of the rim area. The area of thepanel bounded by the flange 44 is provided with raised areas, generallydesignated 50, whereby to form a series of corrugations 52 including anumber of ridges 54 separated by furrows 56. The bottom of each furrowis a panel area 57 coplanar with the rim area 46. Inclined panel areas,designated 60, join the furrows and the ridges. The furrows 56 terminateat each end in an upright panel area 62. Depending from each raised area50 are a number of nozzles 64, each in the form of the frustum of a conedisposed with its base uppermost and its smaller end lowermost. Thenozzles are hollow, of course, and they extend downwardly to a levelbelow the plane of the rim area.

The air diffuser panel is thermoformed, that is, it is molded by placinga sheet of thermoplastic material, in the order of i040 of an inchthick, over a suitably heated die member and drawing the sheet to thedie member by vacuum. After the sheet is thus molded to the shape of thedie, it is removed from the die and the lower ends of the nozzles areopened up.

In the erection of the false ceiling 16, the open frame- Work 26 isarranged preferably with the T-bars 34 and 36 on twenty-four inchcenters thereby to accommodate diffuser panels approximately twenty-fourinches square. The framework 26 may be suspended from the true ceiling14 by hangers 38 or supported in any other suitable manner. Thereupon, adiffuser panel 42 is placed over each opening 40. The rim area 46 seatson the horizontally extending legs of angles 28 or 30 or thehorizontally extending legs of the T-bars 34 or 36, as shown.

The size and number of nozzles per square foot of ceiling area aredetermined -by reference to the performance curves shown in FIGURE 9.For example, for a static pressure of 0.20 inch of water gauge and anair flow of 140 cubic feet per minute per square foot of ceiling area,thirty-six /s-inch-diameter nozzles per square foot of ceiling area are.required. The air is supplied through ducts 22 to the plenum chamber20, from whence it is discharged into the room 18 below through the mazeof nozzles 64 for shower-like delivery in a uniform distribution patternwith a minimum of turbulence.

A ceiling constructed in accordance with the invention provides analmost perfect uniformity of air distribution when air is introduced atonly one end of the room, in rooms up to about 100 feet in length.Heretofore, when a ceiling was constructed of high efiiciencyparticulate air filter units, in accordance with Federal Standard 209,the length of air travel from any one source was limited toapproximately 20 feet from the source.

What is claimed is:

1. In a clean room, the combination comprising upper and lower ceilingsforming an air supply upper plenum chamber, said lower ceiling includingan open framework,

and a plurality of air difiuser panels carried by said framework andcovering the openings therein, each of said panels having a planarperipherally extending rim, sections of the panel area within said rimraised above the plane of the rim thereby to provide panel stiffeningcorrugations, and nozzles depending from said raised sections of thepanel area, said panels conjointly affording a maze of nozzlesdistributed over substantially the entire ceiling area, upper and lowerfloors forming an air discharge lower plenum chamber, said upper floorbeing of open grille type form, means for supplying comparatively largequantities of ventilating air at substantial overpressure to said upperplenum chamber for showerlike delivery thereof through said maze ofnozzles to the room below in a uniform distribution pattern, the airbeing discharged from said room through said upper floor and lowerplenum chamber.

2. The combination according to claim 1 wherein the nozzles are axiallytapered and of a length to extend below the plane of the rim.

3. The combination according to claim 1 wherein each air diffuser panelconsists of a single sheet of thermoplastic material.

4. The combination according to claim 1 wherein the nozzles of eachpanel are uniformly distributed thereover.

5. The combination according to claim 1 wherein the size and number ofnozzles per unit of ceiling area are predetermined for a given pressurein the upper plenum chamber and flow of ventilating air through thenozzles in accordance with the diagram shown in FIGURE 9.

References Cited by the Examiner UNITED STATES PATENTS 2,291,220 7/ 1942Germonprez 98--400 2,807,993 10/ 1957 Ericson 9840 2,912,918 11/1959Mead 98-40 2,962,875 12/1960 Barroero 62-419'X 3,117,427 1/ 1964 Gessel62-419 X 3,252,400 5/1966 Madl 9840 MEYER PERLIN, Primary Examiner.

ROBERT A. OLEARY, Examiner.

W. E. WAYNER, Assistant Examiner.

1. IN A CLEAN ROOM, THE COMBINATION COMPRISING UPPER AND LOWER CEILINGS FORMING AN AIR SUPPLY UPPER PLENUM CHAMBER, SAID LOWER CEILING INCLUDING AN OPEN FRAMEWORK, AND A PLURALITY OF AIR DIFFUSER PANELS CARRIED BY SAID FRAMEWORK AND COVERING THE OPENINGS THEREIN, EACH OF SAID PANELS HAVING A PLANAR PERIPHERALLY EXTENDING RIM, SECTIONS OF THE PANEL AREA WITHIN SAID RIM RAISED ABOVE THE PLANE OF THE RIM THEREBY TO PROVIDE PANEL STIFFENING CORRUGATIONS, AND NOZZLES DEPENDING FROM SAID RAISED SECTIONS OF THE PANEL AREA, SAID PANELS CONJOINTLY AFFORDING A MAZE OF NOZZLES DISTRIBUTED OVER SUBSTANTIALLY THE ENTIRE CEILING AREA, UPPER AND LOWER FLOORS FORMING AND AIR 